[TYPO3-english] powermail does not send mail because of exception of extbase core

[Domi]

Hello,

after update my system I receive following error on my server within 
sending mails via powermail 2.0.2 on TYPO3 4.7.5:

Core: Exception handler (WEB): Uncaught TYPO3 Exception: Parameter is 
not optional | ReflectionException thrown in file 
typo3/sysext/extbase/Classes/Reflection/Service.php in line 459. 
Requested URL: 
http://mydomain.de/index.php?id=9&tx_powermail_pi1%5Baction%5D=create&tx_powermail_pi1%5Bcontroller%5D=Forms&cHash=41593a40ac267c8ffd2de205b9d97193

Weird thing is, that the forms are working on my local server, I 
compared all settings but couldn't find the error.

Any suggestions what runs wrong here?

Thanks,

Dominic